As used herein, the term “integrated circuits” generally refers to monolithic semiconducting devices, such as those formed of group IV materials like silicon or germanium or mixtures thereof, or group III-V compounds such as gallium arsenide. The term “integrated circuits” includes all known configurations of such devices, such as memory and logic, and all designs of such devices, such as CMOS and bipolar.
Typically, many integrated circuits are fabricated on a common substrate, which enables easier handling of the integrated circuits, and other benefits. At the end of the fabrication process, the integrated circuits on the substrate are singulated into individual devices for packaging, further processing, and testing. Defects that originate from the edge of the substrate have a significant impact on device yields. Characterizing the nature of the defect sources in this part of the substrate is difficult to do, due to a lack of review tools and methods to reliably and repeatably navigate to a specific location in this portion of the substrate.
The current state of the art is to scan the edge of the substrate for recognizable features, or to mark the substrate somehow with a feature such as a scratch, a laser dot, or a focused ion beam mark. However, there are many problems associated with the current approaches. For example, at high magnifications it can be difficult to locate or recognize a feature to navigate by. Useful features may not be available in the area of interest, such as around near the back of the substrate. Laser marking or focused ion beam marking equipment is expensive, and often is not available on the equipment where edge review is accomplished. Further, marking tends to not be repeatable between users. In addition, marking can result in defects caused by the marking method itself, which inflicted defects can be confused for the defects being analyzed. Although marking the substrate can enable navigation back to a site to some limited degree, it cannot be used to reference positional locations in a data system where other information about the features of interest is stored.
What is needed, therefore, is a system of referencing substrate edge positions that overcomes problems such as those described above, at least in part.